Semiconductor Device and Method of Manufacturing the Semiconductor Device

ABSTRACT

In a semiconductor device, a first interlayer insulating layer made of an inorganic material and formed on inverse stagger type TFTs, a second interlayer insulating layer made of an organic material and formed on the first interlayer insulating layer, and a pixel electrode formed in contact with the second interlayer insulating layer are disposed on a substrate, and an input terminal portion that is electrically connected to a wiring of another substrate is provided on an end portion of the substrate. The input terminal portion includes a first layer made of the same material as that of the gate electrode and a second layer made of the same material as that of the pixel electrode. With this structure, the number of photomasks used in the photolithography method can be reduced to 5.

This application is a continuation of copending U.S. application Ser.No. 14/719,762 filed on May 22, 2015 which is a continuation of U.S.application Ser. No. 14/179,787 filed on Feb. 13, 2014 (now U.S. Pat.No. 9,041,875 issued May 26, 2015) which is a continuation of U.S.application Ser. No. 12/199,086 filed on Aug. 27, 2008 (now U.S. Pat.No. 8,654,270 issued Feb. 18, 2014) which is a divisional of U.S.application Ser. No. 09/635,945, filed on Aug. 10, 2000 (now abandoned),all of which are incorporated herein by reference).

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a semiconductor device having a circuitstructured by an inverse-stagger type or bottom gate type thin filmtransistor (hereinafter referred to as “TFT”) using a semiconductorfilm, and a method of manufacturing the semiconductor device. Inparticular, the present invention relates to a technique which ispreferably applicable to an electro-optical device represented by aliquid crystal display device and an electronic device on which theelectro-optical device is mounted. In the present invention, thesemiconductor device is directed to all of devices that function usingthe semiconductor characteristics, and the electro-optical device andthe electronic device on which the electro-optical device is mountedfall under the category of the semiconductor device.

2. Description of the Related Art

At present, in a note type personal computer (note personal computer)and a portable information terminal, a liquid crystal display device isemployed for displaying an image or character information. Since anactive matrix liquid crystal display device can obtain a high-fine imageas compared with a passive liquid crystal display device, the activematrix liquid crystal display device is preferably employed for theabove purpose. The active matrix liquid crystal display device isstructured in such a manner that TFTs which function as active elementsare arranged in a matrix in correspondence with the respective pixels ina pixel section. Each of those TFTs are normally formed of an n-channelTFT and controls a voltage which is applied to liquid crystal for eachof the pixels as a switching element to conduct a desired image display.

There is the inverse-stagger type (or bottom gate type) TFT in which theactive layer is formed of an amorphous semiconductor film. The amorphoussemiconductor material is preferably formed of an amorphous silicon filmSince the amorphous silicon film can be formed on a large-area substrateat a low temperature of 300 EC or less, it is considered to be amaterial suitable for mass production. However, the TFT the active layerof which is formed of the amorphous silicon film is small in the fieldeffect mobility to the degree of about 1 cm²/Vsec. Under the abovecircumstances, the drive circuit for conducting the image display isformed in an LSI chip and mounted by a TAB (tape automated bonding)system or a COG (chip on glass) system.

The active matrix liquid crystal display device thus structured iswidely applicable to not only a note personal computer but also a20-inch grade TV system, and demands for high precision and highaperture ratio have been increasingly raised in order to improve theimage quality while a screen size has been large in area. For example, adocument of “The Development of Super-High Aperture Ratio with LowElectrically Resistive Material for High-Resolution TFT-LCDs”, S.Nakabu, et al., 1999 SID International Symposium Digest of TechnicalPapers, pp. 732-735 has reported a technique of manufacturing a liquidcrystal display device which is UXGA (1600×1200) in pixel density and 20inches in-size.

In order to supply and spread the above-mentioned products on market,there are required to improve the productivity and lower the costs whileenhancing the reliability. In the active matrix liquid crystal displaydevice, the TFTs are formed on a substrate by using a plurality ofphotomasks through the photolithography technique. In order to improvethe productivity and also improve the yield, a reduction in the numberof processes is considered as effective means. Specifically, it isnecessary to reduce the number of photomasks required for manufacturingthe TFTs. The photomask is used to form a photo-resist pattern on thesubstrate with a mask during an etching process in the technique of thephotolithography. Therefore, if one photomask is used, there addedprocesses for resist coating, pre-baking, exposing, developing,post-baking, etc., processes for forming a film, etching, etc., whichare conducted before and after the former processes and processes forseparating the resist, cleaning and drying, etc., resulting in acomplicated work.

SUMMARY OF THE INVENTION

The present invention has been made in order to solve the aboveproblems, and therefore an object of the present invention is to realizea reduction of the manufacturing costs and an improvement of the yieldby reducing the number of processes for manufacturing the TFTs in anelectro-optical device and a semiconductor device which are representedby an active matrix liquid crystal display device.

In order to achieve the above object, according to one aspect of thepresent invention, there is provided a semiconductor device, comprising:

a first interlayer insulating layer made of an inorganic material andformed on an inverse stagger type (or bottom gate type) TFT with achannel formation region which is formed of a semiconductor layer havingan amorphous structure on a substrate;

a second interlayer insulating layer made of an organic material andformed on the first interlayer insulating film;

a pixel electrode formed in contact with the second interlayerinsulating layer; and

an input terminal portion formed along an end portion of the substrateand electrically connected to a wiring of another substrate;

wherein the input terminal portion includes a first layer made of thesame material as that of a gate electrode and a second layer made of thesame material as that of the pixel electrode. With the above structure,the number of photomasks used in the photolithography technique isreduced to 5.

According to another aspect of the present invention, there is provideda semiconductor device, comprising:

a first interlayer insulating film made of an inorganic material andformed on an inverse stagger type (or bottom gate type) TFT with achannel formation region which is formed of a semiconductor layer havingan amorphous structure on a substrate;

a pixel electrode formed in contact with the first interlayer insulatingfilm formed on a gate electrode of the TFT; and

an input terminal portion formed along an end portion of the substrateand electrically connected to a wiring of another substrate;

wherein the input terminal portion includes a first layer made of thesame material as that of a gate electrode and a second layer made of thesame material as that of the pixel electrode.

According to still another aspect of the present invention, there isprovided a method of manufacturing a semiconductor device, comprising:

a first step of forming a gate electrode and a first layer of an inputterminal portion which is electrically connected to a wiring on anothersubstrate on a substrate having an insulating surface;

a second step of forming a gate insulating layer on the gate electrode;

a third step of forming a semiconductor layer having an amorphousstructure on the gate insulating layer;

a fourth step of forming a semiconductor layer containing one-conductivetype impurities therein on the semiconductor layer having the amorphousstructure;

a fifth step of forming a source wiring and a drain wiring in contactwith the semiconductor layer containing the one-conductive typeimpurities;

a sixth step of removing parts of the semiconductor layer containing theone-conductive type impurities and the semiconductor layer having theamorphous structure with the source wiring and the drain wiring asmasks;

a seventh step of forming a first interlayer insulating layer made of aninorganic material on the source wiring and the drain wiring;

an eighth step of forming a second interlayer insulating layer made ofan organic material on the first interlayer insulating layer;

a ninth step of selectively removing the first interlayer insulatinglayer, the second interlayer insulating layer and the gate insulatinglayer to expose the first layer of the input terminal portion; and

a tenth step forming an pixel electrode and a second layer of the inputterminal portion on the second interlayer insulating film.

According to yet still another aspect of the present invention, there isprovided a method of manufacturing a semiconductor device, comprising:

a first step of forming a gate electrode and a first layer of an inputterminal portion which is electrically connected to a wiring on anothersubstrate on a substrate having an insulating surface;

a second step of forming a gate insulating layer on the gate electrode;

a third step of forming a semiconductor layer having an amorphousstructure on the gate insulating layer;

a fourth step of forming a semiconductor layer containing one-conductivetype impurities therein on the semiconductor layer having the amorphousstructure;

a fifth step of selectively removing the gate insulating layer to exposethe first layer of the input terminal portion;

a sixth step of forming a pixel electrode and a second layer of theinput terminal portion in contact with the gate insulating layer;

a seventh step of forming a source wiring and a drain wiring in contactwith the semiconductor layer containing the one-conductive typeimpurities;

an eighth step of removing parts of the semiconductor layer containingthe one-conductive type impurities and the semiconductor layer havingthe amorphous structure with the source wiring and the drain wiring asmasks; and

a ninth step of forming a first interlayer insulating layer made of aninorganic material on the source wiring and the drain wiring.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects, features and advantages of this invention willbecome more fully apparent from the following detailed description takenwith the accompanying drawings in which:

FIGS. 1A and 1B are top views and cross-sectional views showingprocesses of manufacturing a pixel TFT and an input terminal portion;

FIGS. 2A and 2B are top views and cross-sectional views showingprocesses of manufacturing the pixel TFT and the input terminal portion;

FIGS. 3A and 3B are top views and cross-sectional views showingprocesses of manufacturing the pixel TFT and the input terminal portion;

FIGS. 4A and 4B are top views and cross-sectional views showingprocesses of manufacturing the pixel TFT and the input terminal portion;

FIG. 5 is a top view and a cross-sectional view showing a process ofmanufacturing the pixel TFT and the input terminal portion;

FIG. 6 is a cross-sectional view showing the structure of a liquidcrystal display device;

FIG. 7 is a cross-sectional view showing the structure in which theliquid crystal display device is mounted;

FIGS. 8A and 8B are cross-sectional views for explanation of thestructure of a gate electrode;

FIG. 9 is a diagram for explanation of a taper structure on an endportion of the gate electrode;

FIG. 10 is a top view for explanation of an arrangement of a pixelportion and an input terminal portion of the liquid crystal displaydevice;

FIGS. 11A and 11B are cross-sectional views for explanation of thestructure of the input terminal portion; and

FIGS. 12A to 12F are diagrams showing examples of the semiconductordevice.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Now, a description will be given in more detail of preferred embodimentsof the present invention with reference to the accompanying drawings.

First Embodiment

A first embodiment of the present invention will be described withreference to FIGS. 1A, 1B, 2A and 2B. This embodiment shows a method ofmanufacturing a liquid crystal display device, and a method of formingan inverse stagger type IF T of a pixel portion on a substrate andfabricating a storage capacitor connected to the TFT will be describedin detail in the order of processes. Also, those figures show a processof fabricating an input terminal portion disposed on an end portion ofthe substrate for electric connection to a wiring of a circuit disposedon another substrate. In FIGS. 1A, 1B, 2A and 2B, portions (I) show topviews whereas portions (II) show cross-sectional views taken along aline A-A′.

Referring to FIG. 1A, a substrate 101 may be made of a glass substratesuch as barium boro-silicate glass or alumino boro-silicate glass whichis represented by #7059 glass or #1737 glass made by Corning Inc.Alternatively, a stainless substrate or a ceramic substrate on which anoxide silicon film a nitride silicon film or the like is formed, etc.,may be employed as the substrate 101.

A gate electrode 102, a gate wiring 102′, a storage capacitor wiring 103and a terminal 104 of an input terminal portion may be desirably made ofa low-resistive electrically conductive material such as aluminum (Al).However, since a single substance of Al suffers from such problems thatit is low in heat resistance and is liable to be corroded, the abovemembers are made of Al combined with a heat-resistant electricallyconductive material. The heat-resistant electrically conductive materialmay be made of an element selected from titanium (Ti), tantalum (Ta) ortungsten (W), an alloy that contains any one of the above elements, analloy film that combines the above elements together, or a nitride thatcontains any one of the above elements. In addition, the above membersmay be made of the combination of only the above heat-resistantelectrically conductive materials.

The selection of the above materials is appropriately determined inaccordance with the screen size of the liquid crystal display device.The heat resistant electrically conductive material which is about 10 Ωin area resistance and about 5 inches or less in screen size isadaptable to the liquid crystal display device. However, the heatresistant electrically conductive material is not always adaptive to theliquid crystal display device of the screen size more than 5 inches.This is because if the drawing-around length of the gate wiringconnected to the gate electrode on the substrate becomes necessarilylarge, a problem of a wiring delay cannot be ignored. For example, inthe case where the pixel density is VGA, 480 gate wirings and 640 sourcewirings are formed, and in the case where the pixel density is XGA, 768gate wirings and 1024 source wirings are formed. The resistance of thegate wirings are determined in accordance with the thickness and thewidth of the wiring in addition to the specific resistance of thematerial to be used, but naturally limited by the combination with theaperture ratio, and since the pixel density becomes higher, fining isrequired. In the case where the screen size of the display region is 13inch class, the length of the diagonal line is 340 mm, and in the casewhere the screen size is 18 inch class, the length is 460 mm. In thiscase, in order to realize the liquid crystal display device, it isnaturally desirable that the gate wiring is made of a low-resistiveelectrically conductive material such as Al.

Therefore, the gate electrode and the gate wiring are made of thecombination of the heat-resistant electrically conductive material withthe low-resistive electrically conductive material. The propercombination of the materials will be described with reference to FIGS.8A and 8B. If the screen size is 5 inches or less, as shown in FIG. 8A,there is applied a structure of laminating an electrically conductivelayer (A) 801 made of nitride of the heat resistant electricallyconductive material and an electrically conductive layer (B) 802 made ofthe heat resistant electrically conductive material. The electricallyconductive layer (B) 802 may be made of an element selected from Al, Ta,Ti or W, an alloy that contains any one of the above elements, or analloy film that combines the above elements together. The electricallyconductive layer (A) 801 is formed of a tantalum nitride (TaN) film, atungsten nitride (WN) film, a titanium nitride (TiN) film or the like.Also, as shown in FIG. 8B, an electrically conductive layer (A) 803 madeof nitride of a heat-resistant electrically conductive material, anelectrically conductive layer (B) 804 made of a low-resistiveelectrically conductive material and an electrically conductive layer(C) 805 made of nitride of a heat-resistant electrically conductivematerial are laminated one on another so as to be adaptive to the largescreen. The electrically conductive layer (B) 804 made of thelow-resistive electrically conductive material is made of a materialcontaining aluminum (Al) and uses 0.01 to 5 atomic % of Al containingscandium (Sc), Ti, silicon (Si) or the like in addition to pure Al. Theelectrically conductive layer (C) 805 has the effect of preventinghillock from occurring in Al of the electrically conductive layer (B)804.

In FIG. 8(A), the electrically conductive layer (A) 801 is set to 10 to100 nm (preferably 20 to 50 nm) in thickness, and the electricallyconductive layer (B) 802 is set to 200 to 400 nm (preferably 250 to 350nm) in thickness. For example, in the case where the W film is formed asthe gate electrode, the electrically conductive layer (A) 801 is formedin thickness of 50 nm with a WN film and the electrically conductivelayer (B) 802 is formed in thickness of 250 nm with a W film byintroducing an Ar gas and nitrogen (N₂) gas through the sputteringmethod with W as a target. However, in order to employ the W film as thegate electrode, it is necessary to lower the resistance, and theresistivity is preferably set to 20 μΩcm or less. The W film can belowered in resistivity by increasing crystal grains. However, in thecase where a large amount of impurity elements such as oxygen arecontained in W, crystallization is impeded to make the resistance high.For that reason, in the case of using the sputtering method, a W targetwith a purity of 99.9999%, and the W film is also formed whilesatisfactorily paying attention to the impurities being not mixed from agas phase at the time of forming a film. In particular, it is betterthat the density of oxygen is set to 30 ppm or less. For example, W canrealize the specific resistance of 20 μΩm or less when the density ofoxygen is set to 30 ppm or less.

On the other hand, in FIG. 8A, in the case where a TaN film is used forthe electrically conductive layer (A) 801, and a Ta film is used for theelectrically conductive layer (B) 802, those films can be formed throughthe sputtering method likewise. The TaN film is formed using a mixturegas of Ar and nitrogen as a sputtering gas and Ta as a target, and theTa film is formed by using Ar as the sputtering gas. Also, if anappropriate amount of Xe and Kr are added in those sputtering gases, theinternal stress of a film to be formed is relieved, thereby beingcapable of preventing the films from being peeled off. The Ta film of anα-phase is about 20 μΩcm in resistivity and can be used as the gateelectrode, but the Ta film of a β-phase is about 180 μΩcm in resistivityand is improper as the gate electrode. Since the TaN film has thecrystal structure close to the α-phase, if the Ta film is formed on theTaN film, the Ta film of the α-phase is readily obtained. In any cases,it is preferable that the electrically conductive layer (B) 802 isformed in the resistivity of 10 to 50 μΩcm.

In the case of the structure shown in FIG. 8B, the electricallyconductive layer (A) 803 is set to 10 to 100 nm (preferably 20 to 50 nm)in thickness, the electrically conductive layer (B) 804 is set to 200 to400 nm (preferably 250 to 350 nm) in thickness, and the electricallyconductive layer (C) 805 is set to 10 to 100 nm (preferably 20 to 50 nm)in thickness. In this example, the electrically conductive layer (A) andthe electrically conductive layer (C) are formed of a WN film or TaNfilm of the heat-resistant electrically conductive material, or a Tifilm, a Ta film, a W film or the like as described above. Theelectrically conductive layer (B) 804 is also formed through thesputtering method and formed of 0.01 to 5 atomic % of Al film containingTi, Si or the like in addition to pure Al.

The gate electrode 102, the gate wiring 102′, the storage capacitorwiring 103 and the terminal 104 are formed by conducting a firstphotolithography process after formation of the electrically conductivelayer on the entire substrate surface, forming a resist mask andremoving an unnecessary portion by etching. In this situation, etchingis conducted in such a manner that a tapered portion is formed on atleast an end portion of the gate electrode 102.

In order to etch the heat-resistant electrically conductive materialsuch as the W film or the Ta film at a high speed and with a highaccuracy and to taper the end portion of the material, the dry etchingmethod using the high-density plasma is proper. In order to obtain thehigh-density plasma, an etching device using micro-waves or inductivelycoupled plasma (ICP) is proper. In particular, the ICP etching device iseasy in the control of plasma and can be adapted to the large area ofthe substrate to be processed. For example, as the specific etchingcondition of the W film, the mixture gas of CF₄ and Cl₂ is used for theetching gas, their flow rates are 30 SCCM, respectively, the dischargepower is 3.2 W/cm² (13.56 MHZ), the substrate bias power is 224 mW/cm²(13.56 MHZ), and the pressure is 1.0 Pa, under the conditions of whichetching is conducted. Under the above conditions, the tapered portionthat gradually increases its thickness inwardly from the end portion ofthe gate electrode 102 is formed at the end portion thereof, and theangle is set to 1 to 20 E, more preferably 5 to 15 E. As shown in FIG.9, the angle of the tapered portion on the end portion of the gateelectrode 102 is an angle of a portion indicated by θ. The angle θ ofthe tapered portion is represented by Tan (θ)=HG/WG using the length(WG) of the tapered portion and the thickness (HG) of the taperedportion.

After the gate electrode 102, the gate wiring 102′, the storagecapacitor wiring 103 and the terminal 104 are formed, an insulating filmis formed on the entire surface to provide a gate insulating layer. Thegate insulating layer 105 is formed of an insulating film 50 to 200 nmin thickness through the plasma CVD method or the sputtering method. Forexample, the gate insulating film 105 is formed of a silicon nitrogenoxide film in thickness of 150 nm. Also, since the silicon nitrogenoxide film fabricated by adding O₂ to SiH₄ and N₂O is reduced in thefixed charge density in the film, it is a preferred material for thisapplication. It is needless to say that the gate insulating layer is notlimited to the above silicon nitrogen oxide film, but may be formed of asingle layer or a lamination structure made of materials of otherinsulating films such as a silicon oxide film, a silicon nitride filmand a tantalum oxide film. For example, in the case of using the siliconoxide film, the gate insulating layer can be formed by mixing tetraethylorthosilicate (TEOS) and O₂ together and conducting electric dischargeat a high frequency (13.56 MHZ) with a power density of 0.5 to 0.8 W/cm²under the conditions where the reactive pressure is 40 Pa and thesubstrate temperature is 250 to 350 EC. The silicon oxide film thusfabricated can obtain an excellent characteristic as the gate insulatinglayer by thereafter thermally annealing the silicon oxide film at 300 to400 EC.

Subsequently, a semiconductor layer having an amorphous structure isformed in thickness of 50 to 200 nm (preferably 100 to 150 nm) on theentire surface of the gate insulating layer through a known method suchas the plasma CVD method or the sputtering method (not shown).Representatively, an amorphous silicon hydride (a-Si:H) film is formedin thickness of 100 nm through the plasma CVD method. The semiconductorlayer having the amorphous structure may be formed of a compoundsemiconductor film having an amorphous structure such as a micro-crystalsemiconductor film or an amorphous silicon germanium film In addition,as a semiconductor layer containing one-conductive type impurityelements therein, an n-type semiconductor film is formed in thickness of20 to 80 nm. For example, an n-type a-Si:H film may be formed, and inorder to form the film, a phosphine (PH₃) 1 to 5% in density is added tosilane (SiH₄). Alternatively, an n-type semiconductor film may be formedof a micro-crystal silicon hidride film (μc-Si:H).

The gate insulating film, the semiconductor layer having the amorphousstructure and the semiconductor layer containing the one-conductive typeimpurity elements are fabricated by a known method, and may befabricated by the plasma CVD method or the sputtering method. Thosefilms can be sequentially formed by appropriately switching over thereactive gas if the plasma CVD method is applied, and by appropriatelyswitching over the target and the sputtering gas if the sputteringmethod is applied. That is, those films can be sequentially laminatedwithout being exposed to the atmosphere by using the same reactivechamber or a plurality of reactive chambers in a plasma CVD device or asputtering device.

The semiconductor layers thus laminated is patterned in a secondphotolithography process so that an island-like semiconductor layer isso formed as to be overlapped with the gate electrode 102. Theisland-like semiconductor layer has an amorphous semiconductor layer 106a and an n-type semiconductor layer 106 b.

Then, an electrically conductive metal layer is formed through thesputtering method or the vacuum evaporation method, a resist maskpattern is formed in a third photolithography process, and a sourcewiring 107, a drain wiring 108 and a storage capacitor wiring 109 areformed by etching as shown in FIG. 2A. Although being not shown, in thisembodiment, the wiring is formed in such a manner that a Ti film isformed in thickness of 50 to 150 nm, brought in contact with the n-typesemiconductor film that forms the source or drain region of theisland-like semiconductor layer, and aluminum (Al) is formed inthickness of 300 to 400 nm on the Ti film, and another Ti film is formedin thickness of 100 to 150 nm on the aluminum film.

Also, in an input terminal portion connected to the source wiring, awiring 110 is formed on the gate insulating layer so as to positionallycoincide with the input terminal portion. Although this appearance isomitted from FIG. 2A, the wiring 110 extends on the gate insulatinglayer and is connected to the source wiring.

Using a source wiring 107 and a drain wiring as masks, the n-typesemiconductor layer 106 b and the amorphous semiconductor layer 106 aare partially removed by etching, to thereby form an aperture 111 in theisland-like semiconductor layer as shown in the part (H) of FIG. 2A. Theaperture 111 allows the n-type semiconductor layer 106 b to be dividedinto a source region 112 and a drain region 113, to thereby form achannel formation region in the island-like semiconductor layer 106 in aself-aligning manner.

Thereafter, as shown in the part (II) of FIG. 2B, a first interlayerinsulating layer 114 made of an inorganic material which covers theaperture 111 and comes in contact with at least a part of the channelformation region is formed on the semiconductor layer having theamorphous structure and the n-type semiconductor layer. The firstinterlayer insulating layer 114 is formed of a silicon oxide film, asilicon nitrogen oxide film, a silicon nitride film or a lamination filmcombining those films together. The thickness of the first interlayerinsulating film 114 is set to 100 to 200 nm. For example, in the casewhere the first interlayer insulating film 114 is formed of the siliconoxide film, the first interlayer insulating film 114 can be formed bymixing TEOS and O₂ together through the plasma CVD method and conductingelectric discharge at a high frequency (13.56 MHZ) with a power densityof 0.5 to 0.8 W/cm² under the conditions where the reactive pressure is40 Pa and the substrate temperature is 200 to 300 EC. Also, in the casewhere the first interlayer insulating film 114 is formed of the siliconnitrogen oxide film, the first interlayer insulating film 114 may beformed of a silicon nitrogen oxide film fabricated by SiH₄, N₂O and NH₃through the plasma CVD method or a silicon nitrogen oxide filmfabricated by SiH₄ and N₂O through the plasma CVD method. In thisexample, the first interlayer insulating film 114 can be formed at ahigh frequency (60 MHZ) with a power density of 0.1 to 1.0 W/cm² underthe conditions where the reactive pressure is 20 to 200 Pa and thesubstrate temperature is 200 to 300 EC. Also, a silicon nitrogenhydrogen oxide film made of SiH₄, N₂O and NH₃ may be applied to thefirst interlayer insulating film 114. Similarly, the silicon nitridefilm can be fabricated by SiH₄ and NH₃ through the plasma CVD method.

In addition, a second interlayer insulating layer 115 made of an organicmaterial and formed on the first interlayer insulating film 114 isformed in the average thickness of 1.0 to 2.0 μm. The organic resinmaterial may be polyimide, acrylic, polyamide, polyimidamide, BCB(benzocyclobutene) or the like. For example, in the case of usingpolyimide of the type where the material is thermally polymerized afterit is coated on a substrate, polyimide is baked by a clean oven at 200to 300 EC to form the second interlayer insulating layer 115. Also, inthe case of using acrylic, a two-liquid material is used, and after amain material and a curing agent are mixed together, the mixed materialis coated on the entire surface of the substrate by using a spinner.Thereafter, the coated material is pre-heated by a hot plate at 80 ECfor 60 seconds, and further baked by a clean oven at 180 to 250 EC for60 minutes, thereby being capable of forming the second interlayerinsulating layer 115.

Since the second interlayer insulating film 115 is made of the organicinsulating material, the surface can be excellently flattened. Also,since the organic resin material is generally low in permittivity, aparasitic capacitor can be reduced. However, since the organic resinmaterial has the hygroscopic property and is not proper for a protectivefilm, it is preferable that the second interlayer insulating film 115 iscombined with the silicon oxide film, the silicon nitrogen oxide film,the silicon nitride film or the like formed as the first interlayerinsulating film 114 as in this embodiment.

Thereafter, a fourth photolithography process is conducted to form aresist mask of a predetermined pattern, thereby forming contact holesthat reaches the source region or the drain region which is defined inthe respective island-like semiconductor layers. The contact holes areformed through the dry etching method. In this case, the secondinterlayer insulating film 115 made of an organic resin material isfirst etched by using the mixture gas of CF₄, O₂ and He as an etchinggas, and thereafter the first interlayer insulating film 114 is etchedby using CF₄ and O₂ as an etching gas. On the input terminal portion,the second interlayer insulating film 115, the first interlayerinsulating film 114 and the gate insulating layer 105 are partiallyetched so that the terminal 104 and the wiring 110 are partiallyexposed.

Then, a transparent electrically conductive film is formed in thicknessof 50 to 200 nm through the sputtering method or the vapor evaporationmethod, and a fifth photolithography process is conducted to form apixel electrode 118 as shown in FIG. 2B. The pixel electrode 118 isconnected to the drain wiring 108 on a connecting portion 116 and alsoconnected to the storage capacitor electrode 109 on a connecting portion117. At the same time, a transparent electrically conductive film 119 isso disposed as to be in contact with at least parts of the terminal 104and the wiring 110. The detail of a cross-sectional view of the sectionB-B′ which is taken along a direction indicated by an arrow in the part(II) of FIG. 2B is shown in FIG. 11A. In the figure, the gate electrode104 is formed of an electrically conductive layer (A) 130 and anelectrically conductive layer (B) 131, and the transparent electricallyconductive film 119 is so formed as to be in contact with at least partsof the electrically conductive layer (A) 130 and the electricallyconductive layer (B) 131. Also, the detail of a cross-sectional view ofthe section C-C′ which is taken along a direction indicated by an arrowin the part (II) of FIG. 2B is shown in FIG. 11B. The wiring 110 is of athree-layer structure consisting of a Ti film 132, an Al film 133 and aTi film 134, and the transparent electrically conductive film 119 is soformed as to be in contact with at least parts of those films. In thisway, the terminal 104 and the wiring 110 are electrically connected toeach other. However, it is unnecessary to dispose the wiring 110 on theinput terminal portion which is connected to the gate wiring, and thetransparent electrically conductive film 119 is so disposed as to be incontact with at least a part of the terminal 104.

The transparent electrically conductive film is formed of indium oxide(In₂O₃), an alloy of indium oxide and tin oxide (In₂O₃—SnO₂, ITO forshort) or the like through the sputtering method, the vapor evaporationmethod or the like. The etching process of those materials is conductedby using the solution of hydrochloric acid. However, since the residueis liable to occur particularly in the etching of ITO, an alloy ofindium oxide and zinc oxide (In₂O₃—ZnO) may be used in order to improvethe etching property. Since the alloy of indium oxide and zinc oxide(In₂O₃—ZnO) is excellent in surface smoothness and also excellent inheat stability as compared with ITO, even if the terminal 104 is formedof an Al film, corrosion can be prevented. Similarly, zinc oxide (ZnO)is also a proper material, and further zinc oxide (ZnO:Ga) to whichgallium (Ga) is added may be employed in order to enhance thetransmittance of the visible light and the electric conductivity.

In this way, an inverse stagger type n-channel TFT 120 and a storagecapacitor 121 can be completed through the five photolithographyprocesses by using the five photomasks. Those TFTs 120 and capacities121 are disposed in a matrix in correspondence with the respectivepixels to form a pixel portion, thereby being capable of providing onesubstrate for manufacturing an active matrix liquid crystal displaydevice. In the present specification, the above substrate is called“active matrix substrate” for convenience.

FIG. 10 is a diagram for explanation of an arrangement of a pixelportion and an input terminal portion of the active matrix substrate. Apixel portion 902 is disposed on a substrate 901, and gate wirings 908and source wirings 907 are disposed on the pixel portion so as to crosseach other. The n-channel TFTs 910 which are connected to the gatewirings 908 and the source wirings 907 are disposed in correspondencewith the respective pixels. The drain side of the n-channel TFT 910 isconnected with one terminal of a storage capacitor 911, and anotherterminal of the storage capacitor 911 is connected to a storagecapacitor wiring 909. The structures of the n-channel TFT 910 and thestorage capacitor 911 are identical with those of the n-channel TFT 120and the storage capacitor 121 shown in FIG. 2B.

One end portion of the substrate is formed with an input terminalportion 905 that inputs a scanning signal, and connected to the gatewiring 908 by a gate wiring 906. Also, another end portion of thesubstrate is formed with an input terminal portion 903 that inputs animage signal and connected to the source wirings 907 by the connectingwiring 904. The number of gate wirings 908, the number of source wirings907 and the number of storage capacitor wirings 909 are plural inaccordance with the pixel density, and their number is described above.Also, an input terminal portion 912 that inputs the image signal and aconnecting wiring 913 may be disposed so that the source wirings arealternately connected to the input terminal portions 912 and 903. Thenumbers of input terminal portions 903, 905 and 912 may be arbitrarilyset and may be appropriately determined by an implementor.

Second Embodiment

A description will be given of a method in which TFTs of the pixelportion are formed in the inverse stagger type on the substrate with astructure different from that in the first embodiment to manufacture thestorage capacitor connected to the TFTs with reference to FIGS. 3A to4B. Similarly, in FIGS. 3A, 3B and FIGS. 4A, 4B, their parts (I) are topviews and cross-sectional views taken along a line A-A′ are shown byparts (II). The active matrix substrate manufactured by this embodimentcorresponds to the transmission-type liquid crystal display device, andhereinafter differences from the first embodiment will be mainlydescribed.

Referring to FIG. 3A, a substrate 201 may be made of a glass substratesuch as barium boro-silicate glass or alumino boro-silicate glass whichis represented by #7059 glass or #1737 glass made by Corning Inc.Alternatively, a stainless substrate or a ceramic substrate on which anoxide silicon film a nitride silicon film or the like is formed on thesurface may be employed as the substrate 201.

A gate electrode 202, a gate wiring 202′, a storage capacitor wiring 203and a terminal 204 of an input terminal portion may be desirably made ofthe combination of a low-resistive wiring material such as Al with aheat-resistant electrically conductive material. Alternatively, they maybe made of the combination of only the heat-resistant electricallyconductive materials. For example, a lamination structure of a WN filmand a W film may be applied. After the electrically conductive layerwith the above structure has been formed on the entire surface of thesubstrate, a first photolithography process is conducted to form aresist mask, and unnecessary portions are removed by etching to formthose components. In this situation, etching is conducted so that atapered portion is formed on at least an end portion of the gateelectrode 202.

The gate insulating layer 205 is formed of a silicon oxide film, asilicon nitrogen oxide film, a silicon nitride film, a tantalum oxidefilm or the like in the thickness of 50 to 200 nm through the plasma CVDmethod or the sputtering method. Subsequently, a semiconductor layerhaving an amorphous structure is formed in thickness of 50 to 200 nm(preferably 100 to 150 nm) on the entire surface of the gate insulatinglayer 205 through a known method such as the plasma CVD method or thesputtering method (not shown). Representatively, an amorphous siliconhydride (a-Si:H) film is formed through the plasma CVD method. Inaddition, as a semiconductor layer containing one-conductive typeimpurity elements therein, an n-type semiconductor film is formed inthickness of 20 to 80 nm. For example, an n-type a-Si:H film may beformed.

Then, a second photolithography process is conducted on thesemiconductor layer thus laminated and formed, and an island-likesemiconductor layer 206 is so formed as to be overlapped with the gateelectrode 202 as shown in FIG. 2B. The island-like semiconductor layer206 has an amorphous semiconductor layer 206 a and an n-typesemiconductor layer 206 b.

Subsequently, as shown in the part (II) of FIG. 4A, a thirdphotolithography process is conducted to remove a part of the gateinsulating film formed on the terminal 204 by etching, thereby definingan aperture 217. Then, the transparent electrically conductive film isformed in thickness of 50 to 200 nm through the sputtering method, thevapor evaporation method, the spray method or the like, and atransparent electrically conductive film 208 is formed on the pixelelectrode 207 and the terminal 217 through a fourth photolithographyprocess.

Thereafter, as in the first embodiment, an electrically conductive layeris formed through the sputtering method or the vapor evaporation method,a resist mask pattern is formed through a fifth photolithographyprocess, and a source wiring 209 and a drain wiring 210 are formed byetching as shown in FIG. 4A. The drain wiring 210 is so formed as to beoverlapped with the pixel electrode 207 on its end portion where thedrain wiring 210 and the pixel electrode 207 are electrically connectedto each other. Also, the connection of the source wiring with the inputterminal portion is made such that an end portion 211 of the sourcewiring extending on the gate insulating film is so formed as to beoverlapped with the transparent electrically conductive film 208 andelectrically connected to the terminal 204.

The n-type semiconductor layer 206 b and the amorphous semiconductorlayer 206 a are partially removed by etching with the source wiring 209and the drain wiring 210 as masks, to thereby form an aperture 212 inthe island-like semiconductor layer as shown in the part (II) of FIG.4B. The aperture 212 allows the n-type semiconductor layer 206 b to bedivided into a source region 213 and a drain region 214, to thereby forma channel formation region in the island-like semiconductor layer 206 ina self-aligning manner.

Thereafter, as shown in the part (II) of FIG. 4B, a first interlayerinsulating layer 215 made of an inorganic material which covers theaperture 212 and comes in contact with at least a part of the channelformation region is formed on the semiconductor layer having theamorphous structure and the n-type semiconductor layer. The firstinterlayer insulating film 215 is formed of a silicon oxide film, asilicon nitrogen oxide film, a silicon nitride film or a lamination filmcombining those films together. The thickness of the first interlayerinsulating film 215 is set to 100 to 200 nm. Then, the first interlayerinsulating layer 215 on the pixel electrode 207 and the transparentelectrically conductive film 208 of the input terminal portion isremoved through a sixth photolithography process.

In this way, an inverse stagger type n-channel TFT 220 and a storagecapacitor 221 can be completed through the six photolithographyprocesses by using the six photomasks. The arrangement of the pixelportion and the input terminal portion in the active matrix substratemanufactured in accordance with this embodiment is identical with thatin the first embodiment as shown in FIG. 10.

Third Embodiment

The second embodiment shows a method of manufacturing an active matrixsubstrate adaptive to the transmission type liquid crystal displaydevice, and a third embodiment shows an example adaptive to a reflectiontype liquid crystal display device.

First, the processes shown in FIG. 3B are conducted in the same manneras that in the second embodiment. Then, as shown in the part (II) ofFIG. 5, a third photolithography process is conducted to remove a partof the gate insulating film disposed on the terminal 204 by etching, tothereby form an aperture 230. Then, an electrically conductive layer isformed through the sputtering method and the vapor evaporation method asin the first embodiment, a resist mask pattern is formed through afourth photolithography process, and a source wiring 231 and a drainwiring 232 are formed by etching as shown in FIG. 5. The drain wiring 32serves as a pixel electrode and is so formed as to be overlapped withthe storage capacitor wiring 203. Also, the connection of the sourcewiring to the input terminal portion is made by electric connection withthe terminal 204 in the aperture 230.

Thereafter, the first interlayer insulating layer 234 made of an organicmaterial is formed as in the second embodiment. The first interlayerinsulating layer 234 on the pixel electrode and the input terminalportion is removed through a fifth photolithography process. In thisway, an active matrix substrate adaptive to the reflection type liquidcrystal display device can be fabricated by using five photomasksthrough the five photolithography process.

Fourth Embodiment

In a fourth embodiment, a description will be given of a process offabricating an active matrix liquid crystal display device from theactive matrix substrate fabricated in the first embodiment. As shown inFIG. 6, an oriented film 600 is formed on an active matrix substratewhich is in a state shown in FIG. 2B. Normally, the oriented film of theliquid crystal display device is frequently made of polyimide resin.

A light shielding film 602, a color filter 603 and a flattening film604, a transparent electrically conductive film 605 and an oriented film606 are formed on a counter substrate 601 opposite to the oriented film600. The light shielding film 602 is made of Ti, Al, chrome (Cr) or thelike and patterned in accordance with the arrangement of TFTs of theactive matrix substrate. Color filters 603 consisting of red, green andblue filters are disposed in correspondence with the respective pixels.The flattening film 604 is formed of an organic resin film and may bemade of the same material as that of the second interlayer insulatingfilm used in the first embodiment. After the oriented film has beenformed, liquid crystal molecules are subjected to a rubbing process soas to be oriented with a given pre-tilted angle.

Then, the active matrix substrate on which the pixel portion is formedand the counter substrate are bonded together through a spacer 607 by asealant 608 containing a spacer 609 therein through a known cellassembling process. As a result, a liquid crystal injection region 610is formed. The liquid crystal material may be a known material andrepresentatively TN liquid crystal. After the injection of the liquidcrystal material, an injection port is sealed with a resin material. Incase of the transmission type liquid crystal display device, polarizingplates 611 and 612 are bonded together to complete an active matrixliquid crystal display device shown in FIG. 6. In case of the reflectiontype liquid crystal display device, the polarizing plate 612 is omitted,and the polarizing plate 611 is disposed on only the counter substrate601 side.

This embodiment shows a method of manufacturing an active matrix liquidcrystal display device on the basis of the active matrix substratefabricated in the first embodiment. However, the active matrix liquidcrystal display device can be fabricated in the same manner even if theactive matrix substrate shown in the second or third embodiment isemployed.

Fifth Embodiment

The active matrix substrate and the liquid crystal display device whichare manufactured by implementing the present invention can be applied tovarious electro-optic devices. Then, the present invention is applicableto all the electronic devices installed with the electro-optic device asa display medium. The electronic device includes a personal computer, adigital camera, a video camera, a portable information terminal (amobile computer, a portable telephone, an electronic document, etc.), atelevision, etc.

FIG. 12A shows a personal computer which is made up of a main body 2001with a microprocessor, a memory and so on, an image input section 2002,a display device 2003 and a key board 2004. The present invention isapplicable to the display device 2003. FIG. 12B shows a video camerawhich is made up of a main body 2101, a display device 2102, a voiceinput section 2103, an operating switch 2104, a battery 2105 and animage receiving section 2106. The present invention is applicable to thedisplay device 2102.

FIG. 12C shows a portable information terminal which is made up of amain body 2201, an image input device 2202, an image receiving section2203, an operating switch 2204 and a display device 2205. The presentinvention is applicable to the display device 2205.

FIG. 12C shows an electronic play device such as a TV game or a videogame, which is made up of an electronic circuit 2308 such as a CPU, amain body 2301 on which a recording medium 2304 is mounted, a controller2305, a display device 2303, a speaker 2307 and a display device 2302installed in the main body 2301. The display device 2303 and the displaydevice 2302 installed in the main body 2301 may display the sameinformation, or the former may serve as a main display device whereasthe latter may serve as an auxiliary display device so as to display theinformation of the recording medium 2304, to display the operating stateof the device, or provided with the function of a touch sensor tofunction as an operating board. Also, in order to mutually transmit asignal among the main body 2301, the controller 2305 and the displaydevice 2303, wire communication may be conducted, or wirelesscommunication or optic communication may be conducted with the provisionof sensor portions 2306 and 2307. The display device 2303 enables itsscreen size to increase up to about 30 inches, and can be employed as atelevision in combination with a tuner not shown.

FIG. 12D shows a player using a recording medium in which program hasbeen recorded (hereinafter referred to as “recording medium”) which ismade up of a main body 2401, a display device 2402, a speaker portion2403, a recording medium 2404 and an operating switch 2405. Therecording medium may be formed of a DVD (digital versatile disc), acompact disc (CD) or the like so as to conduct the reproduction or animage display of a music program, a video game (or TV game), orinformation display through the internet, etc. The present invention ispreferably applicable to the display device 2402 or other signal controlcircuits.

FIG. 12E shows a digital camera which is made up of a main body 2501, adisplay device 2502, an eye-piece portion 2503, an operating switch 2504and an image receiving portion (not shown). The present invention isapplicable to the display device 2502 and other signal control circuits.

FIG. 7 shows an example of a method of mounting the above liquid crystaldisplay device loaded on the electro-optic device. The liquid crystaldisplay device is formed with an input terminal portion 702 on an endportion of a substrate 701 on which TFTs are manufactured, which isformed a terminal 703 a made of the same material as that of the gatewiring as described in the first embodiment and a transparentelectrically conductive film 703 b. Then, the substrate 701 is bonded toa counter substrate 704 with a sealant 705 containing a spacer 706therein, and polarizing plates 707 and 708 are further disposed. Thebonded substrate is fixed to a casing 721 with a spacer 722.

A driving circuit is formed in an LSI chip 713 and mounted in the TABsystem. The driving circuit is formed of a flexible printed circuit(FPC), and FPC is produced by forming a copper wiring 710 in an organicresin film 709 such as polyimide and connected to an input terminal 702with an anisotropic electrically conductive agent. The anisotropicelectrically conductive agent is made up of an adhesive 711 andparticles 712 having an electrically conductive surface several tens toseveral hundreds • in diameter, which are mixed in the adhesive 711 andplated with gold or the like. The particles 712 are brought in contactwith the input terminal 702 and the copper wiring 710 where electriccontact is formed. In order to enhance the mechanical strength of thatportion, a resin layer 718 is formed.

The LSI chip 713 is connected to the copper wiring 710 with a bump 714and sealed with a resin material 715. Then the copper wiring 710 isconnected to a printed substrate 717 on which a signal processingcircuit, an amplifier circuit, a power supply circuit and so on aredisposed on a connecting terminal 716. In the transmission type liquidcrystal display device, a light source 719 and an optically conductivemember 720 are disposed on the counter substrate 704 and used asback-light.

Although being not shown in the above examples, the present invention isapplicable to a navigation system, a portable television, and so on. Asdescribed above, the present invention is very widely applied andapplicable to the electronic devices in any fields. The above electronicdevices of this embodiment can be realized by using the techniques ofthe first to fourth embodiments.

The foregoing description of the preferred embodiments of the inventionhas been presented for purposes of illustration and description. It isnot intended to be exhaustive or to limit the invention to the preciseform disclosed, and modifications and variations are possible in lightof the above teachings or may be acquired from practice of theinvention. The embodiments were chosen and described in order to explainthe principles of the invention and its practical application to enableone skilled in the art to utilize the invention in various embodimentsand with various modifications as are suited to the particular usecontemplated. It is intended that the scope of the invention be definedby the claims appended hereto, and their equivalents.

What is claimed is:
 1. (canceled)
 2. A display device comprising: apixel portion comprising a plurality of pixels over a first substrate,each of the plurality of pixels comprising: a thin film transistorcomprising a gate electrode, a semiconductor layer, and a firstinsulating layer between the gate electrode and the semiconductor layer;a source wiring in electrical contact with the semiconductor layer; adrain wiring in electrical contact with the semiconductor layer; a pixelelectrode, wherein a portion of one of the source wiring and the drainwiring is in contact with an upper surface of the pixel electrode; asecond insulating layer comprising an inorganic material over the pixelelectrode, the source wiring and the drain wiring; a terminal portioncomprising: a first conductive layer over the first substrate, the firstconductive layer comprising the same material as the gate electrode; aninsulating layer over the first conductive layer; a transparentconductive layer over the insulating layer, wherein the transparentconductive layer is in contact with an upper surface of the firstconductive layer; and a second substrate opposed to the first substrate.3. The display device according to claim 2, wherein the pixel electrodeis transparent.
 4. The display device according to claim 2, wherein thetransparent conductive layer is formed from a same starting film as thepixel electrode.
 5. The display device according to claim 2, wherein theinorganic material of the second insulating layer is a silicon nitridefilm.
 6. An electronic device having the display device according toclaim 2, the electronic device is one selected from the group consistingof a personal computer, a digital camera, a video camera, a mobilecomputer, a portable telephone, an electronic document, and atelevision.
 7. The display device according to claim 2, furthercomprising a source region and a drain region over the semiconductorlayer.
 8. The display device according to claim 2, wherein the displaydevice is a liquid crystal display device.
 9. An electronic devicehaving the display device according to claim 2, the electronic devicefurther comprises a flexible printed circuit attached to the terminalportion.
 10. The display device according to claim 2, wherein thesemiconductor layer is a silicon film.
 11. The display device accordingto claim 2, wherein the semiconductor layer is an amorphous siliconfilm.
 12. A display device comprising: a pixel portion comprising aplurality of pixels over a first substrate, each of the plurality ofpixels comprising: a gate electrode; a semiconductor layer adjacent tothe gate electrode; a first insulating layer between the gate electrodeand the semiconductor layer; a source wiring on and in electricalcontact with the semiconductor layer; a drain wiring on and inelectrical contact with the semiconductor layer; a pixel electrode onand in contact with the first insulating layer, wherein a portion of oneof the source wiring and the drain wiring is in contact with an uppersurface of the pixel electrode; a second insulating layer comprising aninorganic material over the pixel electrode, the source wiring and thedrain wiring, and a terminal portion comprising: a first conductivelayer over the first substrate, the first conductive layer comprisingthe same material as the gate electrode; an insulating layer over thefirst conductive layer; a transparent conductive layer over theinsulating layer, wherein the transparent conductive layer is in contactwith an upper surface of the first conductive layer.
 13. The displaydevice according to claim 12, wherein the pixel electrode istransparent.
 14. The display device according to claim 12, wherein thetransparent conductive layer is formed from a same starting film as thepixel electrode.
 15. The display device according to claim 12, whereinthe inorganic material of the second insulating layer is a siliconnitride film.
 16. An electronic device having the display deviceaccording to claim 12, the electronic device is one selected from thegroup consisting of a personal computer, a digital camera, a videocamera, a mobile computer, a portable telephone, an electronic document,and a television.
 17. The display device according to claim 12, furthercomprising a source region and a drain region over the semiconductorlayer.
 18. An electronic device having the display device according toclaim 12, the electronic device further comprises a light sourceadjacent to the display device, wherein the display device is a liquidcrystal device.
 19. An electronic device having the display deviceaccording to claim 12, the electronic device further comprises aflexible printed circuit attached to the terminal portion.
 20. Thedisplay device according to claim 12, wherein the semiconductor layer isa silicon film.
 21. The display device according to claim 2, wherein thesemiconductor layer is an amorphous silicon film.